My interpretation of the four seasons in human life:
Spring means new beginnings and many new choices. These choices give us a universe of freedom.
Summer means new adventures, the moment when we choose our path and plunge into new things.
Fall is a nostalgic season, time is running out, it is a time to look back and reflect.
Winter represents the end, it is sad and bleak, but from that end we see new beginnings sprout; and life comes full circle.